It is well known in the art to extract a component such as an oil from a solid material by grinding the material to form grains or flakes and then passing a solvent through the granular material to separate the extractable component via solvent extraction. Commonly, the granular material is processed in batches. In one form of operation, the batches of the granular material, such as soybeans, are fed into cells or baskets near a feed station. The cells move along a circular path from the feed station toward a discharge station, where the processed granular material is discharged. Miscella, or solvent which has passed at least once through the granular material, drains from the cells by gravity and collects in pans beneath the cells for reuse or discharge.
In order to extract the desired component as completely as possible from the granular material, it is common to expose the granular material to solvent or miscella at multiple fluid feed stations along the circular path. For example, it is known to introduce the miscella into the cells in a "counterflow" fashion such that the miscella is collected after it has percolated through the solid material. Pure solvent is introduced at the last fluid feed station along the circular path, while miscella drained from a cell at the first fluid feed station along the circular path is collected and discharged to an evaporator or the like to effect isolation of the desired material.
Once the extraction process has been completed, the granular material must be collected and conveyed out of the system. It is common to discharge the granular material out of the cells into a hopper at the end of the extraction process. Unfortunately, the granular material (which is still at least wet with the solvent) tends to stick to the sides of the hopper or to aggregate. As a result, the granular material often fails to flow smoothly to a screw or other conveyor at the bottom of the hopper. In some systems, agitators are provided to loosen the granular material so that it flows smoothly to the bottom of the hopper. Such agitators, which are typically motorized, add to the expense and maintenance requirements of the extractor.
Even after discharge of the solid material into the discharge hopper or the like, unrecovered miscella still exists therein.
Additionally in those extraction systems in which the cells are supported for rotation around a central, vertically disposed axial shaft, axial support bearings that are located in or adjacent to miscella drainage reservoirs as the granular material carrying cells are susceptible to contamination so that the extraction units must be shut down periodically for cleaning.
Accordingly, there remains a need in the art for the provision of an extractor having a discharge unit constructed in such manner as to minimize the tendency of the discharged solid material from agglomerating at the discharge area or along discharge chute walls and the like. There is an even more specific need to provide a discharge device that provides for improved miscella removal.
Additionally, in those structures in which rotatable baskets are structured for rotation about a centrally disposed axial shaft, there is a need to provide a thrust bearing to journal the shaft, which bearing is located remote from the miscella collection receiver and the grain carrying cells so as to minimize the possibility of bearing contamination.